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  Discussion on Research Summary: Compares the efficacy of the three available WNV vaccines
Author Message
Moderator:
DrO

Posted on Thursday, Sep 13, 2007 - 10:42 am:

This is a very good study that compares the three commercially available vaccines for West Nile Virus:
1) The Fort Dodge product, an inactivated (K-WN) WNV vaccine
2) Merial's product, a modified-live vaccine (CP-WN), containing the WNV prM and E proteins expressed by a canarypox vector
3) Intervet's product a live-chimera vaccine (WN-FV) containing WNV prM and E proteins expressed in a YF17D vector.

This testing found that the Intervet product protected within 28 days of the primary vaccination while the other products are recommended as a two injection primary series. THough all vaccines were effective those given the Intervet product had fewer and less severe clinical signs. Based on this study the Intervet product appears superior to the other commercially available products.
DrO

Clin Vaccine Immunol. 2007 Aug 8;
28 Day Vaccine Efficacy in Equine WNV Encephalitis Model.

Seino KK, Long MT, Gibbs EP, Bowen RA, Beachboard SE, Humphrey PP, Dixon MA, Bourgeois MA.
Using a severe challenge model that produces clinical West Nile Virus (WNV) disease, the efficacy of three commercially available equine WNV vaccines was tested in horses. Twenty-four healthy, WNV-seronegative horses of varying ages and gender were placed into three randomized, blinded trial groups consisting of eight horses with two horses in each group receiving 1) an inactivated (K-WN) WNV vaccine, 2) a modified-live vaccine (CP-WN), containing the WNV prM and E proteins expressed by a canarypox vector 3) a live-chimera vaccine (WN-FV) containing WNV prM and E proteins expressed in a YF17D vector, or 4) diluent control. Challenge by this model caused grave neurological signs, viremia, moderate to severe histopathologic lesions in the brain and spinal cord, and an outcome of 0% survivorship in all six control horses. In contrast, challenge in horses at between 28 days post-vaccination of the chimera vaccine or 56 days post vaccination of the commercial inactivated or modified-live vaccines resulted in 100% survivorship, protection from the onset of WN encephalitis and viremia. Horses vaccinated with the live-chimera vaccine showed significantly fewer clinical signs than horses vaccinated with inactivated vaccine (p=0.035) and the control horses (p</= 0.01). Mild residual inflammatory lesions were seen in a few of the vaccinated horses.

For more information see the article on West Nile Virus.
Member:
teddyj1

Posted on Thursday, Sep 13, 2007 - 6:45 pm:

Hey All, OK, so we have a better WNV vaccine, but have any of you experienced the problem of availability of the "Vaccine of choice" from your particular Vet.? I have had great difficulty in being able to get the Vaccine I prefer to use from my Vet. practice, or better yet, any one Vet practice; meaning, who ever is the Vet's main Pharmaceutical Rep, seems to be directly related, in many cases as to what vaccine brand they use, not necessarily the best vaccine....
Dr. O do you or any other members have any suggestions regarding how to get the safest, most effective vaccines with out having to go to individual Vet's for individual vaccines ! (Don't worry I wouldn't do that)
I hope I'm not the only person out there noticing this phenomena(LOL)
Thanks TOD
Moderator:
DrO

Posted on Friday, Sep 14, 2007 - 7:15 am:

You should discuss this issue with your veterinarian as there are several reasons beside efficacy why a vaccine is chosen. Some may choose to wait awhile to see if the new chimera technology has any unexpected consequences, I once heard a veterinarian say when I was a student, never be the first nor the last to use a new product. Remember the older vaccine is 90% effective and though efficacy of the new vaccine better, with one injection, but the long term outcome is not clearly better with this vaccine yet. It will take time to generate that information.

Risk certainly effects vaccine choice. Though I use the most efficacious respiratory disease vaccines in young show horses for middle age trail horses I am very comfortable with the less expensive injectable killed, it saves them 10 or 20 bucks for very low risk problems that I want to offer some protection.

Another consideration is putting together a combination of vaccines that minimizes injections and reactions. This is a particular problem with our newest most innovative vaccines because they are all single injections: If we singly injected each vaccine that would be 8 injections instead of the three I currently give.

Some is just inertia and increased difficulty maintaining stock of many different brands of vaccine. If your areas is at high risk of WNV and certainly if you are vaccinating in the face of an outbreak, you should push for the new product but expect a significantly higher cost. However in areas where the risk for WNV is low use of the older FD product is a reasonable response from an epidemiological (cost vs benefit) stand point.
DrO
Member:
teddyj1

Posted on Friday, Sep 14, 2007 - 10:06 am:

Thanks Dr. O, you make very good,prudent points. I will certainly keep all of this in mind.


TOD
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